US9616607B2 - Process for producing microporous polyolefin film - Google Patents

Process for producing microporous polyolefin film Download PDF

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US9616607B2
US9616607B2 US14/369,941 US201314369941A US9616607B2 US 9616607 B2 US9616607 B2 US 9616607B2 US 201314369941 A US201314369941 A US 201314369941A US 9616607 B2 US9616607 B2 US 9616607B2
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film
polyolefin
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extraction
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Tetsuro Nogata
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
    • B29C47/0057—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/0025—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching
    • B01D67/0027—Organic membrane manufacture by inducing porosity into non porous precursor membranes by mechanical treatment, e.g. pore-stretching by stretching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
    • B01D67/003—Organic membrane manufacture by inducing porosity into non porous precursor membranes by selective elimination of components, e.g. by leaching
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • B29C47/0021—
    • B29C47/8805—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
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    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
    • B29C48/914—Cooling of flat articles, e.g. using specially adapted supporting means cooling drums
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/0009—After-treatment of articles without altering their shape; Apparatus therefor using liquids, e.g. solvents, swelling agents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/20—Manufacture of shaped structures of ion-exchange resins
    • C08J5/22—Films, membranes or diaphragms
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H01M2/145—
    • H01M2/1653—
    • H01M2/18—
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/403—Manufacturing processes of separators, membranes or diaphragms
    • H01M50/406—Moulding; Embossing; Cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/463—Separators, membranes or diaphragms characterised by their shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/15—Use of additives
    • B01D2323/20—Plasticizers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
    • B29C71/0009—After-treatment of articles without altering their shape; Apparatus therefor using liquids, e.g. solvents, swelling agents
    • B29C2071/0027—Removing undesirable residual components, e.g. solvents, unreacted monomers
    • B29C47/8845—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B29K2023/04—Polymers of ethylene
    • B29K2023/06—PE, i.e. polyethylene
    • B29K2023/0608—PE, i.e. polyethylene characterised by its density
    • B29K2023/065—HDPE, i.e. high density polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/0005—Condition, form or state of moulded material or of the material to be shaped containing compounding ingredients
    • B29K2105/0038—Plasticisers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/04—Condition, form or state of moulded material or of the material to be shaped cellular or porous
    • B29K2105/041—Microporous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29L2031/00—Other particular articles
    • B29L2031/34—Electrical apparatus, e.g. sparking plugs or parts thereof
    • B29L2031/3468—Batteries, accumulators or fuel cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the field relates to a method for manufacturing a polyolefin microporous film that is ideally used as, e.g., a filter membrane or a separator for various batteries and capacitors. More specifically, the field relates to a method for manufacturing a polyolefin microporous film in which high-speed solvent drying is implemented, enabling high-speed continuous productivity and allowing superior quality and uniformity to be obtained.
  • Electrolytic fluids, positive and negative electrode active materials, and other agents are used in lithium-ion secondary cells. Therefore, a polyolefin-based polymer, particularly polyethylene or polypropylene, which is inexpensive, is typically used as the material for the separator, taking chemical resistance into account. Characteristics such as electrode short-circuit prevention, high ion permeability, ease of assembly and processing during winding of the cell, cell safety, and reliability have conventionally been desired as basic functions of separators applied in lithium-ion secondary cells and other cells employing a non-aqueous electrolyte. Uniform quality has also been greatly needed in recent years as the size, energy density, and output of cells have increased.
  • Well-known methods for manufacturing polyolefin microporous films involve melt-kneading a composition composed of a polyolefin resin and a plasticizer; extruding the composition from a die and molding the composition into a film form; after extrusion, stretching the film uniaxially or biaxially; after stretching, using a solvent to extract the plasticizer from the film; drying the solvent; and, as necessary after drying, further stretching or heat-treating (Japanese Laid-Open Patent Application No 5-156058, Japanese Laid-Open Patent Application No. 11-60789, Japanese Laid-Open Patent Application 2010-235707).
  • a well-known method for drying of the solvent after extraction of the plasticizer involves drying on drying rolls such that the width of the film is mechanically restrained, and the speed of the drying rolls is 35 to 50 m/min (Japanese Laid-Open Patent Application 2011-42805).
  • Patent Document 1 refers to; Japanese Laid-Open Patent Application No. 5-156058.
  • Patent Document 2 refers to: Japanese Laid-Open Patent Application No. 11-60789.
  • Patent Document 3 refers to Japanese Laid-Open Patent Application 2010-235707.
  • Patent Document 4 refers to Japanese Laid-Open Patent Application 2011-4280.
  • a method for manufacturing a polyolefin microporous olefin film comprises: (a) a step for melt-kneading a composition containing at least a polyolefin film and a plasticizer, extruding the kneaded composition from a die, and molding the extrudate into a film form; (b) a step for stretching the obtained film in at least one direction after the extruding and molding; (c) a step for extraction by using a solvent to extract and thereby remove the plasticizer from the film after the stretching; and (d) a step for drying the film after the extraction, the method for manufacturing a polyolefin microporous film being characterized in that the film is brought into close contact with a roll set to a temperature lower than a boiling point of the solvent after the extraction step and before the drying step; and a liquid lacking an affinity for polyolefin and being of a temperature equal to or greater than the boiling point of the solvent is brought into contact with
  • the method comprises: (a) a step for melt-kneading a composition containing at least a polyolefin film and a plasticizer, extruding the kneaded composition from a die, and molding the extrudate into a film form; (b) a step for stretching the obtained film in at least one direction after the extruding and molding; (c) a step for extraction by using a solvent to extract and thereby remove the plasticizer from the film after the stretching; and (d) a step for drying the film after the extraction, the method for manufacturing a polyolefin microporous film being characterized in that a width of the film is mechanically restrained after the extraction step and before the drying step; and a liquid lacking an affinity for polyolefin and being of a temperature equal to or greater than a boiling point of the solvent is brought into contact with the film while the mechanical restraint of the width of the film is maintained, where
  • FIG. 1 is a schematic diagram of a drying device used in Example 1 of the present invention.
  • FIG. 2 is a schematic diagram of a drying device used in Example 2 of the present invention.
  • FIG. 3 is a graph of the distribution of thickness and porosity of the microporous film obtained in Example 1 of the present invention.
  • FIG. 4 is a graph of the distribution of thickness and porosity of the microporous film obtained in Example 2 of the present invention.
  • FIG. 5 is a graph of the distribution of thickness and porosity of the microporous film obtained in Comparative Example 1 of the present invention.
  • FIG. 6 is a graph of the distribution of thickness and porosity of the microporous film obtained in Comparative Example 2 of the present invention.
  • FIG. 7 is a graph of the distribution of thickness and porosity of the microporous film obtained in Comparative Example 3 of the present invention.
  • Patent Document 1 As ideal drying methods; however, specifically, methods for blowing hot air on heating rolls, where the heating devices can be readily constructed, came to be widely employed.
  • the present inventors brought a liquid heating medium into contact with the film while maintaining the film in a state of adhesion to a low-temperature roll or maintaining a state of mechanical restraint on the width of the film, whereby the film is heated and dried, whereby a solution for the aforementioned problems was discovered, and the inventors arrived at the present invention.
  • a first aspect of the present invention is a method for manufacturing a polyolefin microporous film, comprising (a) a step for melt-kneading a composition, extruding the kneaded composition from a die, and molding the extrudate into a film form, the composition containing at least a polyolefin resin and a plasticizer; (b) a step for stretching the obtained film in at least one direction after the extruding and molding; (c) a step for using a solvent to extract and thereby remove the plasticizer from the film after the stretching; and (d) a step for drying the film after the extraction, the method for manufacturing a polyolefin microporous film being characterized in that the film is brought into close contact with a roll kept at a temperature lower than a boiling point of the solvent after the extraction step and before the drying step; and a liquid lacking an affinity for polyolefin and being of a temperature equal to or greater than the boiling point of the solvent is brought into
  • a second aspect of the present invention is a method for manufacturing a polyolefin microporous film, comprising (a) a step for melt-kneading a composition, extruding the kneaded composition from a die, and molding the extrudate into a film form, the composition containing at least a polyolefin resin and a plasticizer; (b) a step for stretching the obtained film in at least one direction after the extruding and molding; (c) a step for using a solvent to extract and thereby remove the plasticizer from the film after the stretching; and (d) a step for drying the film after the extraction, the method for manufacturing a polyolefin microporous film being characterized in that a width of the film is mechanically restrained after the extraction step and before the drying step; and a liquid lacking an affinity for polyolefin and being of a temperature equal to or greater than a boiling point of the solvent is brought into contact with the film while the mechanical restraint of the width of the film
  • the film is brought into close contact with a low-temperature roll, or the width of the film is mechanically restrained, and drying is performed while maintaining that state, whereby the film can be prevented from contracting in the widthwise direction due to the drying.
  • the temperature of the roll In cases where the film is brought into close contact with a roll, the temperature of the roll must be lower than the boiling point of the solvent. When the temperature of the roll is greater than or equal to the boiling point of the solvent, the solvent rapidly vaporizes, and the film is not able to be brought into close contact with the roll, which is therefore undesirable.
  • a clip-type tenter device is preferable as means for mechanically restraining the width of the film. Any method for mechanically restraining both edge parts while the film is in close contact with the roll may be used.
  • a liquid lacking affinity with polyolefins is used as a heating medium, and the heating medium is brought into contact with the film at a temperature greater than or equal to the boiling point of the solvent, whereby the film is heated, and the solvent is evaporated, removed, and dried.
  • the film is heated directly using a high-temperature liquid, whereby adequate heat can be imparted to the film in a short time, and the drying time can be contracted. Since a liquid heating medium is used for the heating, even if, hypothetically, undried portions detach from the roll, the heating efficiency does not decrease, and high-speed drying can be implemented.
  • a liquid lacking affinity with polyolefins is selected as the heating medium, whereby the heating medium does not enter into the film, and even if, hypothetically, a small amount of the heating medium does enter the film, negative pressures resulting from the Laplace force will be generated due to the lack of affinity with the polyolefin, and the pores will not be crushed.
  • the liquid that lacks affinity with the polyolefin and is used as the heating medium is preferably water, because water has a large specific heat.
  • a polyolefin microporous film of the present invention high-speed continuous productivity is enabled, decreases in porosity resulting from contraction of the film can be prevented, and the uniformity of porosity and film pressure can be improved. Lax alignment of the polyolefin during drying is also minimized, and decreases in strength can be prevented.
  • Embodiments of the present invention will be described in detail below.
  • Homopolymers or copolymers of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, or other olefins can be used as the polyolefin used in the present invention.
  • high-density polyethylene is preferable in being inexpensive and in reaching a high degree of crystallization as a result of significant stretching.
  • the plasticizer used in the method is a non-volatile solvent that when mixed together with the polyolefin resin allows a uniform solution to be formed at or above the melting temperature of the polyolefin resin.
  • Specific examples include liquid paraffin, paraffin wax, and other hydrocarbons; dioctyl phthalate, dibutyl phthalate, and other esters; and oleyl alcohol, stearyl alcohol, and other higher alcohols.
  • liquid paraffin and paraffin wax are particularly preferable in being readily obtained and easily handled.
  • any ratio of the polyolefin resin and the plasticizer used in the present invention is acceptable as long as the ratio is sufficient for microphase separation to occur and for a microporous film to be formed after extraction and removal of the plasticizer.
  • the polyolefin resin content is 10 to 70 wt %, and particularly preferably 20 to 50 wt %.
  • Melt-kneading of the polyolefin resin and the plasticizer is preferably performed by normal methods using a multi-screw extruder, a single-screw extruder, or the like.
  • antioxidants may be added to the composition composed of the polyolefin resin and the plasticizer.
  • the melt-kneaded resin composition is molded into the form of a sheet or film (both referred to as “film form” below) using extrusion.
  • Extrusion may involve extruding a film form using a T-die (flat die) or using a circular die or the like to extrude a tubular shape, which is then worked into a film form.
  • the thickness of the film after extrusion is preferably 1 to 500 ⁇ m, and particularly preferably 5 to 100 ⁇ m. Strength readily becomes insufficient when the film is too thin, and, when used as a cell separator or the like, the occupied volume of the separator may become too large when the film is too thick.
  • the extruded film is stretched along at least one axial direction.
  • “Stretching in at least one axial direction” means uniaxial stretching in the machine direction, uniaxial stretching in the width direction, simultaneous biaxial stretching, or sequential biaxial stretching. Stretching is not limited to a single stage but may involve multi-stage or repeated stretching. The stretching method is not particularly limited but may involve roll stretching or stretching using a tenter. Biaxial stretching is particularly preferable in order to implement high strength.
  • the stretching temperature may be any temperature used in routine methods. Stretching is performed [at a temperature] in a range, e.g., less than or equal to the melting temperature (Tm) of the polyolefin resin composition and greater than or equal to (Tm ⁇ 50)° C.
  • the draw ratio is not particularly limited. In the case of uniaxial stretching, the draw ratio is preferably a factor 2 to 20 and particularly preferably 4 to 10. In the case of biaxial stretching, the area magnification is usually a factor of 2 to 400, and particularly preferably 4 to 200.
  • the extraction solvent used in the present invention should be a poor solvent for the polyolefin and a favorable solvent for the plasticizer, and should have a boiling point lower than the melting point of the polyolefin resin.
  • the boiling point of the solvent is more preferably below 100° C.
  • a solvent for cases in which the plasticizer is liquid paraffin or paraffin wax include n-hexane, cyclohexane, and other hydrocarbons; methylene chloride, 1,1,1-trichloromethane, and other halogenated hydrocarbons; ethanol, isopropanol, and other alcohols; tetrahydrofuran, ethyl ether, and other ethers; and acetone, methylethyl ketone, and other ketones.
  • methylene chloride or cyclohexane is particularly preferable in being easy to obtain and handle.
  • the film After extraction of the plasticizer and before the drying step, the film is brought into close contact with a cooling roll, or the width of the film is mechanically restrained.
  • the surface temperature of the cooling roll should be less than or equal to the boiling point of the solvent and such that the solvent does not significantly condense.
  • the solvent is methylene chloride
  • 0 to 40′C. is preferable, and near 35° C., is more preferable.
  • the method of mechanical restraint preferably involves a tenter device for using a plurality of clips to grip both edge parts of the film and to cause the clips to move along with the motion of the film.
  • a method for using a belt-shaped object to hold both edge parts of the film when the film is in close contact with a roll can also be used to mechanically restrain the width of the film.
  • the film After bringing the film into close contact with a cooling roll or mechanically restraining the width of the film, the film is brought into contact with a liquid heating medium and thereby heated, and the solvent dried, while maintaining the adhesion to the cooling roll or the restraint of the film width.
  • the liquid used as the heating medium must not have an affinity for the polyolefin. Since the liquid used as the heating medium does not have an affinity for the polyolefin, the heating-medium liquid does not enter into the polyolefin microporous film.
  • the liquid used as the heating medium is preferably water.
  • the boiling point of the heating-medium liquid is greater than or equal to the boiling point of the extraction solvent.
  • the method for bringing the heating-medium liquid into contact with the film may involve immersing the film in the heating medium, passing the film through a tank filled with the heating-medium liquid, spraying the heating medium onto the film, or the like.
  • the film is preferably sprayed from the side of the surface opposite the side of the conveying roll.
  • solvent on the roll surface may rapidly vaporize, and the film may detach from the roll.
  • a polyolefin resin material resulting from dry-blending 0.3 parts by weight of 2,6-di-t-butyl-p-cresol into 100 parts by weight of high-density polyethylene (weight-average molecular weight: 300,000; ratio of weight-average molecular weight to number-average molecular weight: 7; density: 0.956)) and 70 parts by weight of liquid paraffin (kinematic viscosity: 75.9 cSt at 37.78° C.) were melt-kneaded using a biaxial extruder.
  • the resin mix was extruded from a flat die (coat-hanger die) onto a cooling roll controlled to have a surface temperature of 40° C., and a sheet-form microporous film precursor having a width of 1.1 mm was obtained.
  • the resulting sheet-form microporous film precursor was next stretched 5 ⁇ 5 times at 119° C. using a tenter-type simultaneous biaxial stretching machine, and a film-shaped microporous-film precursor having a uniform width of 1000 mm and a uniform thickness of the 40 ⁇ m was obtained.
  • the resulting film-shaped microporous-film precursor was brought into contact with methylene chloride (solvent) via counter-flow for approximately two hours, and the liquid paraffin (plasticizer) was extracted and removed.
  • methylene chloride solvent
  • paraffin plasticizer
  • the film was heated and dried at a film-production speed of 70 m/min using the drying device of FIG. 1 .
  • a polyethylene microporous film 1 from which liquid paraffin was extracted and removed was brought into close contact with a cooling roll 3 , which was controlled to have a temperature of 35° C. at a point 2 .
  • Hot water at a temperature of 65° C. was sprayed nozzles 4 while adhesion was maintained, and the methylene chloride was heated and removed.
  • a Litematic VL-50A-B (contact point number: 120060) made by Mitutoyo was used to measure the thickness at a pitch of 10 mm in the widthwise direction using the widthwise center of the microporous film as a reference.
  • Example 1 Other than a drying process in which 50° C. hot air was blown on a 40° C. heating roll at a film-production speed of 10 m/min, [Comparative Example 1 was made] in the same manner as Example 1.
  • the widthwise distribution of the thickness and porosity of the resulting microporous film are shown in Table 1 and FIG. 5 .
  • Comparative Example 2 was made in the same manner as Comparative Example 1.
  • the widthwise distribution of the thickness and porosity of the microporous film thus obtained are shown in Table 1 and FIG. 6 .
  • Example 3 Other than using a film-production speed of 20 m/min and not using the tenter 13 to mechanically restrain [the film] in the widthwise direction, [Comparative Example 3 was made] in the same manner as Example 2.
  • the widthwise distribution of the thickness and porosity of the microporous film thus obtained are shown in Table 1 and FIG. 6 .
  • a microporous film having uniform thickness and porosity can be obtained in the method of the present invention even when the film-production speed is 70 m/min or 120 m/min.
  • a microporous film having a uniform thickness and porosity was obtained if the film-production speed was low at 10 m/min (Comparative Example 1), but at a film-production speed of 20 m/min, the variation in the thickness and porosity became severe, and the uniformity of quality and the stability were significantly negatively impacted (Comparative Example 2).
  • Even in the method for immersing in hot water in cases where there was no mechanical restraint in the widthwise direction, the contraction in the widthwise direction was great, and variation in thickness and porosity became severe.
  • the method can be used in the high-speed production of a polyolefin microporous film used as filter membranes, separators in various types of cells and capacitors, and the like.

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
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  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
  • Cell Separators (AREA)
  • Filtering Materials (AREA)
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KR20170118241A (ko) * 2014-08-29 2017-10-24 스미또모 가가꾸 가부시키가이샤 다공질층, 다공질층을 적층하여 이루어지는 세퍼레이터, 및 다공질층 또는 세퍼레이터를 포함하는 비수 전해액 이차 전지
JP5914789B1 (ja) * 2014-11-18 2016-05-11 東レバッテリーセパレータフィルム株式会社 ポリオレフィン微多孔膜、電池用セパレータおよびその製造方法
US10486112B2 (en) * 2014-11-18 2019-11-26 Toray Industries, Inc. Microporous polyolefin film, separator for battery, and production processes therefor
PL3231837T3 (pl) * 2014-12-11 2022-12-19 Toray Industries, Inc. Mikroporowata folia poliolefinowa, separator do baterii i sposoby ich wytwarzania
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KR102452099B1 (ko) * 2015-03-27 2022-10-11 데이진 가부시키가이샤 복합막의 제조 방법 및 복합막의 제조 장치
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WO2017018483A1 (ja) * 2015-07-29 2017-02-02 東レバッテリーセパレータフィルム株式会社 電池用セパレータおよびその製造方法
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KR20180090998A (ko) * 2015-12-04 2018-08-14 도레이 카부시키가이샤 전지용 세퍼레이터 및 그 제조 방법
JP6645516B2 (ja) * 2015-12-24 2020-02-14 東レ株式会社 ポリオレフィン微多孔膜、電池用セパレータおよびそれらの製造方法
KR102210309B1 (ko) * 2016-06-08 2021-01-29 가부시키가이샤 인비젼 에이이에스씨 재팬 비수전해질 이차 전지
TWI716496B (zh) * 2016-11-21 2021-01-21 日商東麗股份有限公司 電池用隔膜及其製造方法以及電池用隔膜之捲繞體
JP7055663B2 (ja) * 2017-03-03 2022-04-18 住友化学株式会社 フィルム製造方法、セパレータ製造方法および可塑剤製造方法
JP7072623B1 (ja) * 2020-11-11 2022-05-20 芝浦機械株式会社 抽出乾燥装置

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CN104066781B (zh) 2016-08-24
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JP5832907B2 (ja) 2015-12-16
US20140361457A1 (en) 2014-12-11

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